Unity Manual

Using Depth Textures

It is possible to create Render Textures where each pixel contains a high-precision Depth value. This is mostly used when some effects need the Scene’s Depth to be available (for example, soft particles, screen space ambient occlusion and translucency would all need the Scene’s Depth). Image Effects often use Depth Textures too.

Pixel values in the Depth Texture range between 0 and 1, with a non-linear distribution. Precision is usually 32 or 16 bits, depending on configuration and platform used. When reading from the Depth Texture, a high precision value in a range between 0 and 1 is returned. If you need to get distance from the Camera, or an otherwise linear 0–1 value, compute that manually using helper macros (see below).

Depth Textures are supported on most modern hardware and graphics APIs. Special requirements are listed below:

Depth Texture Shader helper macros

Most of the time, Depth Texture are used to render Depth from the Camera. The UnityCG.cginc include file contains some macros to deal with the above complexity in this case:

UNITY_TRANSFER_DEPTH(o): computes eye space depth of the vertex and outputs it in o (which must be a float2). Use it in a vertex program when rendering into a depth texture. On platforms with native depth textures this macro does nothing at all, because Z buffer value is rendered implicitly.

UNITY_OUTPUT_DEPTH(i): returns eye space depth from i (which must be a float2). Use it in a fragment program when rendering into a depth texture. On platforms with native depth textures this macro always returns zero, because Z buffer value is rendered implicitly.

COMPUTE_EYEDEPTH(i): computes eye space depth of the vertex and outputs it in o. Use it in a vertex program when not rendering into a depth texture.